If you are the only primalist and you've got an archon with you then the pseudo support is the best choice because it is basically a DPS gain for the whole raid. The spec also does pretty good damage. If you don't have an archon, you should play a full-fledged mystic support.

Wouldn't the mystic build posted by Jsjoe (with the mystic Flaring Power) as a reply to Hokhmah's spec be a better pick these days?

If you can melee all the time it's better, but if you need to be range at some point during the fight , the dervish one parse a bit higher , around 40 to 70k on average. And you have no cast time so easier for moving part with dervish one too.
Overall , for me , dervish support spec have a better QoL playstyle.

-> Any detailed informations about how Fury points effect Fury Blast? It says: Deals increased damage the closer you are to full Fury when cast.
I wonder what the fury / dmg % ratio is. If it's a linear or exponential gain.

you can assume the damage boost from 40 fury to 100 fury is between 2 times and 2.5 times the damage depending on the number of multiplier you add to fury blast. => 2.48 time the damage

here without any other source of increased damage ( left with 40 fury , right at 100)

=> 1.84 time the damage

Here i only used Scything strike (85% damage boost) before each FB ( left is 40 again and right 100 fury)

=> 2.5 time the damage

And last one (left again 40 fury right 100 fury) , FB boosted with everything we got in the melee spec so SS (85%) + RotB (100%) + MW (90%) , i didn't go full cunning for the eternal proc since the eternal proc isn't that much for FB ( around 100k more on the max hit , 50k on average hit).

What i mean with 2 FB is that you cycle FB and MW faster than they might need to be (8 sec FB dot) so going MW 40pt fb 100pt fb withing the Mw uptime might be a gain and also makes the 100pt fb dot overwrite the 50pt one. ?